Apparatus for transferring cable circuits



Aug. 20, 1940. D. FISHER ET AL APPARATUS FOR TRANSFERRING CABLE CIRCUITSFiled 001:. 25, 1939 the cable.

7 30 cable or a section of old cab-1e.

40 points.

Patented Aug. 20, 19 40 Donald Fisher, Elizabeth, George Blaine Parker,East Orange, Lloyd L. Parker, Ridgewocd, and John Phillip Meehan,Harrington Park, N. J., assignors to American Telephone and TelegraphCompany, a corporation of New York Application October 25, 1939, SerialNo. 301,284

7 Claims.

This invention relates to electrical circuits and systems. Thisinvention also relates to testing circuits and systems as well as toarrangements for identifying the various conductors of a cable. Moreparticularly, this invention relates to methods and means fortransferring the circuits of one cable to those of another cable withoutinterfering wit-h transmission over the various circuits.

"10 In cable systems it is frequently important to identify many of theconductors of a cable at two or more points along the cable withoutinterfering with transmission over those conductors being identified orover any other conductors of In order to accomplish this, it has beenheretofore proposed that a high frequency signal be applied to eachconductor to be identified at one point along the cable and that at oneor more identifying points along the cable the signal be picked up by aprobing device placed in proximity to the conductor carrying the signal.A signal particularly suitable for this purpose, especially in cablescarrying currents of a broad range of frequencies, including highfrequencies, may be a current of a frequency higher than that used fortransmission over any of the conductors of the cable.

It is often necessary, in practice, to substitute a new cable or asection of a new cable for an old As a first step in this process, theindividual conductors of the old and new cables are properly identifiedand then a selected conductor of the old cable is bridged across thereplacing conductor-in the new 35 cable at two transfer points along thecable. Then the splicers at the two transfer points check theconnections with each other over a telephone circuit established betweenthem'and they then cut the conductor in the old cable at the two Thusthe circuit through the new cable is established.

Experience has proven, however, that this transfer operation wasfrequently made erroneously, especially because of misunderstandings 45between the workmen in their telephone instructions to each other. Anyerror of this kind necessarily interrupts service over some of thecircuits extending through the cable. Theinterruption of servicefrequently lays up the various 50 circuits for some considerable timeand this is therefore highly undesirable and at the same time costly.

One of the objects of this invention. is therefore toprovide-arrangements for the transference 55 of the circuits from theconductors of one cable to the conductors of another cable withouterror,

and hence without any interruption whatever of service through thecable.

Another of the objects of this invention is to insure that each circuitprovided through a con- 5 ductor of the new cable is complete over aterm porary path before the corresponding conductor of the old cable issevered. It is also important to see that the circuit provided throughthe conductor of the new cable is complete over the '10 new path beforethe temporary path is removed. Briefly, it is an object of thisinvention to replace one section of cable by another section of cable,maintaining the continuity of each cir- I cuit through the cablethroughout the process of replacement and establishing the accuracy ofeach replacement by signals which are readable at both ends of the cablesection.

This invention and its further objects and features will bebetterunderstood from the detailed .20 description hereinafter followingwhen read in connection with the accompanying drawing showing oneembodiment of the invention merely for the purpose of illustration.

Referring to the drawing, the reference char- 25 acter O designates avacuum tube which may form part of an oscillation generator. ,The gridcircuit of the tube 0 includes the upper portion of a coil L1 as well asa resistor R1, the midpoint of the coil L1 being grounded. The outputcircuit of the tube 0 includes a coil L2 which may be the primarywinding of a transformer T1, a

battery B1, one terminal of which is grounded and the resistor R1. Someof the current flowing in the output circuit of the tube 0 iselectromagnetically. fed back to the in ut circuit through a pathincluding a condenser C1, a resistor R2, the lower portion of the coilL1 and ground. The two portions of coil L1 which are divided by thepoint at which the coil is grounded are, of course, 1 coupledelectromagnetically to each other and hence produce an effect in theinput circuit of the tub-e O for the purpose of generating oscillations,as is. well understood in the art. The coil L1 is shunted by acondenserC2 which may be variable, as illustrated, for the purpose of controllingthe frequency ofthe oscillations generated by the oscillation generator.The oscillation generator just described may be of any other type wellknown in the art but is preferably one which is capable of generating alow frequency current as, for example, a current of cycles.

Thecoil L3 is the secondary winding of the transformer T1. This coil isconnected near its upper terminal to the primary winding L4 of ,55

another transformer T2. The lower terminal of coil L3 may-be adjustablyconnected to a conductor E0 which may be one of the conductors of acable Q1 extending between two points which are widely spaced from eachother. At the distant end of the cable, a clip Y1 may be used toestablish a connection between the conductor E0 and one of the otherconductors such as E1 of the cable Q1. This same conductor of the cablewhich is designated E1 at the near end, may be connected by means of acircuit including a clip Y2 to any desired point along the coil L4 oftransformer T2. The adjustability'of the connections to coils L3 and L4are useful in initially setting up the circuit, but they need not beadjustable in practice.

The secondary winding L5 of the transformer T2 is bridged by a condenserC's which may also be adjustable, as illustrated, so as to tune thecircuit to the particular current generated by the circuits attached tothe tube 0. The tuned circuit just referred to is also bridged by apotentiometer P which is used as a gain-control device for controllingthe level of the current transmitted to an amplifier tube designated A.The control grid of the amplifier tube A is connected to the adjustableterminal of the potentiometer P. The screen .grid of the tube A issupplied with a suitable potential obtained at point V along the batteryB1. The output circuit of the tube A includes a coil L6, battery B1 andresistor R3. The output circuit of the tube A may also be tuned by meansof a condenser such as that designated C4 which may be adjustable if sodesired.

The current amplified by the amplifier tube A may be fed through acondenser C5 to the grid of a detector tube D. The detector tube D maybe of any well-known type but is preferably a gas-filled tube of theThyratron type. One form of such a tube is sold under the trade name ofRaytheon RK-62. Such a tube will yield a larger plate current change fora given change in grid voltage than is available with the usual vacuumtube. The detector D is operated as a grid leak detector, the leakresistor R4 being connected between the grid of the tube D and ground.The condenser C5 blocks the flow of direct current from the battery B1to the grid of tube D.

The detected current will fiow through the output circuit of the tube D,this circuit including the winding of a relay W1, a coil L7, avariableresistor R5, a meter M, the battery B1 and resistor Re. Theresistor R5 may be adjusted so that when none of the current of theoscillation generator O is supplied to the detector tube D, asubstantial current will flow through the plate circuit of the tube Dand hence operate the relay W1. When the locally generated current isimpressed upon the grid circuit of the detector tube D, however, a highnegative bias will be built up on the grid of the detector tube D whichwill thereupon reduce the current through the winding of relay W1 of theoutput circuit of the tube D. Under such circumstances, the reducedcurrent will be so small as to release the armature of the relay W1. v

A condenser Cs is bridged across the winding of relay W1. The lattercondenser is also part of afilter circuit which includes the winding L1.The capacitance and inductance of the filter circuit are such that theywill act to prevent the transmission of current within a certain rangeof frequencies which might otherwise traversethe selective circuitsalready described. The filter circuit may, for example, be employed tosuppress currents corresponding to telegraph signals of large amplitudetransmitted through the cable circuits and thereby prevent the operationof relay W1 in response to such currents.

The relay W1 may be used to control the operation of a buzzer Z1 as wellas of a relay W2 which is located atthe distant end of the cablesection. The winding of relay W2 may be connected, for example, inparallel with the buzzer Z1. When the relay W1 is released as, forexample, when the oscillation generator 0 supplies current which isamplified by the amplifier A, the buzzer Z1 will be operated, thecircuit of the buzzer Z1 including the armature and back contact ofrelay W1, battery B2 and ground. At the same time, the winding of relayW2 which is connected in parallel with the buzzer Z1 by means ofconductors E11 and E12 will also be 0perated. The conductors E11 andE12-may be, and usually would be, a spare pair within the cable Q1. Theoperation of the relay W2, in turn, will cause the operation of thebuzzer Z2 which is also located at the distant end of the cable station.The circuit of buzzer Z2 will include a battery B3 and the armature andfront contact of the relay W2.

The current generated by the oscillator 0 is supplied through coils L3and L4 of transformers T1 and T2 to two conductors, either or both ofwhich may be within the cable Q1 (or cable Q2) One of these conductorsmay be the conductor E0 and the other of the conductors may be that oneto which the clips Y1 and Y2 are connected. Ii?

the circuit over the two conductors of cable just referred to iscompleted, then the current generated by the oscillator 0' will be fedto the amplifier tube A. Otherwise, the current generated by oscillator0 will fail to reach the amplifier tube A. If the generated currentreaches tube A and is: amplified thereby, it will be detected by tube Dand then cause the relay W1 to release. The release of relay W1 willthereafter cause the simultaneous operation of the. buzzers Z1 and Z2 asalready pointed out hereinabove. If, however, the circuit which includesthe conductor E0 and that conductor to which the clips Y1 and Y2 areboth connected is incomplete,

or if the circuit formed by the two conductors has a very substantialimpedance-an impedance which is greater than a predetermined valuethecurrent, if any, amplified by the amplifier and detected by the tube Dwill be insufiicient to release the relay W1. In that event, the relayW1 E will remain operated and its armature will be separated from itsback contact. This will prevent the two buzzers Z1 and Z2 fromoperating.

Thus, one of the features of this invention consists in the provision ofa circuit coupling the oscillator O with the amplifier-detector which isof low impedance and this low impedance coupling circuit must becompleted before the amplifier-detector will. operate. The completion ofthe coupling circuit is established through two of theconductors,'either or both of which may form part of the cable circuitas already explained.

Let us assume that the cable section Q1 is the old cable section whichis to be replaced .by a newer cable section Q The various conductors E1,E2, E3, E4, etc., of the cable Q1 may be identified and 'marked by tabsS with apparatus of the type shown and described in a copendingapplication of George. B. Parker et al., Serial No.

til

265,574, filed April 1, 1939,.entitled Systems and methods foridentification of conductors The conductors E1, E2, E3, E4 aredesignated at the distant end of. the cable by the reference characters7 E, E,;, E5, and E1, etc. at which point they will also be marked ortabbed. Similarly, the conductors E21, E22, E23,. E24, etc.,-of the newsection of cable Q2 may be similarly identified and marked at thedistant point at which these conductors are designated Es; s, a et inthe drawing.

After the conductors of the two cable sections are properlyidentified,the clips Y1 and Y2 are then connected to opposite terminalsof any one the coupling circuit extending to the windings L3 and L4 ofthe transformers T1 and T2. If this circuit is completed, both buzzersZ1 and Z2 will be sounded. The splicers may then simultaneously cut theconductor of the old cable at the two terminals as, for example, atthepoints X adjacent the tabs S. When the conductor is cut, the couplingcircuit including coils L3 and L4 will be opened and the relay W1 willthen be operated. This, in turn, will remove the battery B2 from thebuzzer Z1 as Well as from the winding of relay W2. Hence both buzzers Z1and Z2 will release.

The conductor E21 ar of the new cable may then be connected at points Xin place of the conductor Il -E;

Thisv will again close the coupling circuit including coils L3 and L4and the buzzers Z1 and Z2 will again operate. When proper buzzer signalshave indicated to the workmen that the transfer operations are correctand complete, the clips Y1 and Y2 will then be removed and the buzzerswill cease to operate. This same process will be repeated for eachconductor to be transferred.

The use of the arrangement above described provides a continuity ofoperation and by means of the buzzers assures the splicers that noerrors have been made in picking up previously identifled conductors andconnecting them into service. The arrangement provides the splicers withautomatic supervision over the transfer operations, the signalsindicating the status of the Various steps in the operation.

The transformer T1 may be arranged so that the impedance ratio maybegfor example, about forty or fifty thousand to one. The transformer T2will, however, be reversed so that the impedance ratio is, for example,one to about a thousand or fifteen hundred. These impedance ratios are,of course, given merely for the purpose of illustration and are utilizedto provide a very low impedance coupling circuit.

It has been pointed out hereinabove that the frequency of the currentgenerated by the circuits connected to the tube may be, for example, 35cycles. This frequency has been successfully used in certaininstallations of the apparatus of this invention. of course, any etherfrequency may be used with the apparatus.

85-cycle current, however, lies predominantly above the telegraphfrequencies ordinarily assigned to cablev circuits and below theordinary voice frequencies. The level of the generated currents must below enough so as not to introduce interference into the telegraph ortelephone circuits.

The low impedance in the circuit coupling the oscillator O with theamplifier A prevents false operation of the transfer set. In the eventthat 'the connections through clips Y1 and Y2 are erroneouslyestablished to points other than those of the very same conductor, thebuzzers will fail to operate. This latter provision insures a positivecheck on the identification of the various conductors of a cable.

An arrangement set up in accordance with this invention may have animpedance between the clipsYi and Y2 of, for example, 5 ohms or less, toall telephone or telegraph currents. This inipedance may be measured atthe lower terminals of COilS L3 and L4. working circuits completedthrough clips Y1 and Y2 will be insuflicient to appreciably interferewith transmission over these working circuits.

While the arrangement described hereinabove may be used to transfer thecircuits extending through the conductors of one cable to thoseextending through the conductors of another cable, the same arrangementand process may be used to transfer the circuits from" certain of theconductors within a cable sheath to other conductors within the samecable sheath.

While this invention has been shown and described in certain particulararrangements merely for the purpose of illustration, it will beunderstood that the general principles of this invention may be appliedto other and widely varied organizations without departing from thespirit of the invention and the scope of the appended claims.

What is claimed is: v

1. Apparatus for transferring the circuits of the conductors of onecable to those of another cable without interfering with service overany of said circuits, comprising a source of alternating current, adetector, and means for coupling said source with said detector, saidcoupling means including a low impedance circuit to which the variouscable conductors are connected one at a time, the alternating currentemanated from said source flowing over the particular conductor 5connected into the coupling means.

2. Apparatus for substituting the conductors of one cable section forthe conductors of another cable section without interfering withtransmis sion of signals over the circuits of said conductors,

comprising an oscillator, a detector, means for coupling the oscillatorwith the detector, said coupling means including a circuit of low im-.

pedance, said circuit including the various cable conductors connectedthereto one at a time, and signal devices located at the two terminalsof The 2 The small unbalance to the said cable sections, said signaldevices being connected to said detector.

3. Apparatus for substituting the conductors of one cable section forthose of another cable section without interruption of service over anyof the circuits connected to said conductors, comprising a source ofalternating current, a detector located together with said source at oneterminal of the cable section, means for coupling said source with saiddetector, said coupling means comprising a circuit which includes thevarious conductors of the cable section connected thereto one at a time,and signaling devices located at the two terminals of the cable section,said devicesbeing responsive to the detected currents.

4. Apparatus for substituting the conductors of one group for those ofanother group without any interruption of service over any of thecircuits connected. to said conductors, comprising an oscillator, anamplifier, a circuit for coupling the amplifier to the oscillator, adetector for rectifying the amplified current, said coupling circuitincluding low impedance windings, said low impendance windings beingconnected in a series circuit including one of the cable conductors.

5. Apparatus for transferring the circuits of the conductors of onecable section to those of another cable section without interfering withthe service over said circuits, comprising a signal device located atone of the terminals of the cable section, the apparatus at the otherterminal of the cable section including an oscillator, an amplifier, adetector coupled to the amplifier, a low impedance circuit coupling theoscillator to the amplifier, said low impedance circuit including aconductor Within the cable section which extends between the twoterminals there- .of, and a signal device controlled by the detector,

another cable section without interfering with the transmission ofsignals over said circuits,

comprising an oscillatona detector including a selective circuit whichtransmits only currents emanating from said oscillator, the frequency ofthe current generated byv the oscillator being so chosen as not toconflict with those frequencies transmitted over the circuits of thecable conductors, a low impedance circuit for coupling the oscillatorwith the detector, said low impedance I circuit including one of thecable conductors conf nected thereto as a series element, two signaldevices located at the two terminals of the cable section, both signaldevices being coupled to the detector, and a filter circuit interposedbetween the detector and the signal devices forpreventing the operationof the signal devices by currents which may traverse the selectivecircuit'of the detector but do not emanate .from the oscillator.

7. Apparatus for progressively transferring the various circuits of theconductors of one cable section to those of another cable sectionwithout interfering with the transmission of signals over the variouscircuits, comprising an oscillator, a detector, a low impedance circuitcoupling the oscillator with the detector, said coupling circuitincluding the various conductors of the cable section which areprogressively connected in DONALD FISHER. GEORGE BLAINE PARKER. LLOYD L.PARIQER.

JOHN PHILLIP MEEHAN.

